Because of the reduction of the fossil fuel resources, nowadays nuclear energy is important for many human societies. Building the Nuclear Power Plants near beaches may increases the possibility of entering the radioactive substances into these environments. In order to prevent the irrecoverable effects of the radionuclides leakage on the environment, it is necessary to determine the concentration of these substances in the aquatic environments. For this purpose different numerical models have been developed to simulate the dispersion of radionuclides in marine environments. In this research the 2D depth averaged hydrodynamic model has been used to obtain the current components in a part of Persian Gulf by applying the tidal effects. The equations solved by finite differentials approach. In this model the time step is 5 seconds and spacial step is 10 kilometers. The results of modelling show that the main stream is to east and east north of Persian Gulf. Also the velocity of water in central region of Persian Gulf and near east open boundary is bigger than other places. Using the averaged velocity of currents obtained from hydrodynamic equation and water avaraged depth in the region, the concentration of 137 C has been calculated by CROM code.